Has anyone considered using a POSA style carburetor on their engine? I
   recall the older Lake Injector carbs receiving their share of bad press
   due
   to the sensitivity of the floatless system to head pressure. While this is
   a
   problem on gravity feed fuel system, using a very low pressure import
   type
   electric fuel pump would eliminate the tuning complications as fuel levels
   changed.
   To my understanding, here is a list of the core components needed for such
   a
   system to properly work;

   1 Either a AeroCarb
   http://www.aeroconversions.com/products/aerocarb/index.html or Revmaster


  http://www.revmasteraviation.com/products/revflow_injector_carburetor/index.htm

   carburetor. Cost is $395 and $330 respectively.

   2 Custom intake manifold. I can't really guess a price but since the POSA
   style carbs can be mounted as downdraft, sidedraft or updraft, you would
   have more design flexibility and potentially save some money.
   3 Very low pressure electric fuel pump. Units like the Mr. Gasket 42S
   http://beta.summitracing.com/parts/MRG-42S/, Professional Products 10701

   http://beta.summitracing.com/parts/PFS-10701/ and Facet 40105
   http://www.aircraftspruce.com/catalog/eppages/facetpumps.php would work
   and
   keep the costs reletively low at $37, $40 and $32 respectively.

   4 Very low pressure fuel regulator such as the Mr. Gasket 9710
   http://beta.summitracing.com/parts/MRG-9710/ for $26 or Holley 12-804
   http://beta.summitracing.com/parts/HLY-12-804/ for $28.
   This list excludes items such as fuel filters, gascolator, fuel lines,
   etc.
   due to their universal nature.
   Plumbing a carburetor heat system should be easier since the carb can be
   mounted in different orientations and much less critical since POSA
   carburetors lack venturi.
   Vlad

   We looked at it for a long long time.
   They are very susceptible to vapor lock as the fuel pressure
   is down around 1 psi. Even the VW guys don't recommend them any more :
   Go with a float bowl. Float bowl Carbs have it all. Mass airflow sensor,
   fuel pressure regulator and fuel injector all rolled up into one :

   Paul Lamar

  Vlad,
  The POSA was the original slide carb, then came the Aero Carb copy of the
  POSA and some other carb was further developed by someone leaving Aero
  Carb
  or so I have been told. The Aero Carb looks good and the flat ground
  needle is the way to go IMHO, however no two needles are the same from what
  I have read on the internet discussion groups. This is Ok for a single carb
  on a single rotor but would need some care in matching the needles in a 2
  carb set-up.

  Aero Carb recommend 35mm for up to 120hp and 38 mm for up to 160hp - no
  venturi.

  Revmaster 40mm carb will flow 166cfm at 10"water

  Edelbrock recommends 42mm for up to 125hp.
  Mukuni recommends 48mm  42 venturi for anything over 120hp

  38mm Lectron carbs flows 161cfm at 10" water
  40mm 186cfm at 10"water
  44 flows 217cfm at 10"water

  All carbs without a float bowl require low fuel boost pump.

  Can't remember all the different carbs and their venturi sizes, but appears
  a venturi does two things- increases inlet speed and acts at a restrictor
  at
  some point.

  It was a fun exercise I didn't find anything that was exactly what I
  wanted,
  so started making my own- and still not finished.
  George down under



Wow George, I'm very impressed with the homework you've done. Seeing as
you're far more acquainted with the design, can I ask you a couple of
questions? I understand that the POSA style was first designed to be gravity
feed only and it seems that the more recent companies aero & revmaster are
still keeping up with that tradition. Why can't the carb be designed to
operate with higher fuel pressures? I don't mean EFI range pressures, but at
least the common 4-7psi range associated with most domestic carbs Holley
2300 for instance. Even if the 4-7psi range is too high for whatever
fundamental reason, perhaps the 1-4psi import range could be used. Do you
have any pictures or specs of your little project? In any case, thanks for
the interesting info.
Vlad


OK guys I am going to give you the basic data to see if
low pressure non float bowl carbs are going to work well in aircraft engines.
Do your homework and ask questions later. Then write an article on low
pressure carbs.

------------------------------------------

Here is a better chart of fuel flow.

Paul Lamar